I had such a great response to my recent commentary that I thought it would be worth the time to take an in-depth look at the implications of such a massive undertaking.

Now that we know it’s physically possible for solar photovoltaics (PV) to supply all of the electricity needs in Kentucky by covering only one-fifth of the land already cleared by mountaintop removal (MTR) with solar panels, I think it’s important to ask this question: How quickly could we make the transition from coal to solar? How much would it cost in the short and long term? How would this transition affect coal mining jobs and how many jobs would it create? Can our economy, and our environment for that matter, afford to stick with coal for the long term?

I think the only way to make a transition of this scale possible would be to spread it over many decades. In my previous assessment, I estimated that it would take a 69.1 GW solar array to provide all of the electricity needs in Kentucky today, but if this project is spread out over many years, the size of the solar array would need to grow to match the expected increase in electric kWh consumption over time.

Figure 1 below shows what I believe would be a feasible transition from coal-fired electricity to solar PV over the next 50 years. If we start by adding roughly 1 gigawatt of solar each year and increase that amount by 7% per year for 40 years, we could achieve a net-zero carbon economy by the year 2050, powered entirely by solar PV. It also shows the expected increase in electricity consumption from a total of about 90 terawatt-hours (TWh) today to about 240 TWh in the year 2060. This increased consumption is based on the U.S. Department of Energy’s data that shows an average annual increase of around 2% in electricity consumption in Kentucky from 1980-2005. (Editor's note: there are a lot of charts in the story, so keep scrolling down.)

Figure 2 below shows the solar PV capacity that would need to be installed per year and the cumulative total in direct current (DC) megawatts. There would be a drop-off in the year 2050 as we achieved net-zero. But new panels would still need to be manufactured and installed as the industry standard 25-year warranty would expire on earlier solar panels, thereby providing long-term jobs. However, manufacturers claim that solar PV panels can function well past their expiration date, producing electricity for 40 or even 50 years.

Figure 3 below shows the jobs that would be created over the next 50 years. This projection is based on a University of California report that claimed that in the solar industry, "20 manufacturing and 13 installation/maintenance jobs [are created] per installed megawatt." As you can see, the 20,000 coal-mining jobs (represented in red in the graph) in Kentucky would pale in comparison to the potential of solar PV. In fact, more than 30,000 jobs could be created in year one with the installation of 1 GW of solar, already matching coal-mining employment. These would not be temporary jobs, either. The maintenance jobs would be needed indefinitely and the manufacturing and installation jobs would be needed as some solar panels are retired and replaced by new panels.

Starting with my estimate from my last commentary, Figure 5 below shows the decrease in the cost per watt DC of installing solar PV and energy storage over the next 50 years. This is based on the fact that the cost per watt to install solar has historically decreased by about 4% per year over that past decade. Energy storage would not need to be added until solar PV electricity production exceeded around 10% of the total, at which point the volatile nature of solar energy can present issues to a stable grid.

Figure 6 below shows the cost per year in dollars to install solar PV, install energy storage, maintain the massive solar array, and build transmission grid infrastructure to get the electricity to residential, commercial and industrial consumers in Kentucky. I used this estimate of $1.5 million per mile to build the high voltage DC (HVDC) transmission lines and estimated an average of 100 miles per line with a maximum of 2,000 MW for each line. As you can see, the annual payroll for solar manufacturers, solar installers, and solar maintenance jobs could be close to $13 billion a year by 2060, providing much-needed employment income to the Commonwealth.

Figure 7 shows the decrease in the consumer price per kilowatt-hour (kWh) for solar energy over time. This cost includes the cost to install solar, install energy storage (beginning in 2020), maintain the solar array, and building the transmission infrastructure. While this decrease may not look like much at first glance, it’s much more desirable than the dramatic cost increases in Figure 8 if we were to stick with coal.

Figure 8 below shows the expected increasing cost of coal-fired electricity, which is sharply different from the expected decreasing cost of solar PV electricity over the same time period. This projection is based on the 5% per year increase in the cost per kWh in Kentucky over the past 10 years for residential, commercial, and industrial sectors in Kentucky from empirical data from the U.S. Energy Information Administration.

Figures 9 and 10 show how costly it could be for Kentucky to ignore to potential of solar energy. While the annual cost of electricity during the transition from coal to solar could be similar to the cost of coal electricity by itself through the year 2030, the exponential increase in coal electricity could drain nearly $150 billion more per year than solar energy by 2060, with a cumulative cost of $1.78 trillion over 50 years. Kentucky has always used the cheap cost of coal electricity to lure business to the commonwealth; the same strategy could be used for solar electricity if we get a head start on competing states.

Figures 11, 12 and 13 show the environmental benefit of using solar PV electricity. It’s clear that solar energy is superior to coal-fired electricity in this department. Imagine using solar electricity to manufacture solar panels right here in Kentucky!

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Dan Hofmann is President of RegenEn Solar LLC (www.regenensolar.com), a solar panel installation company located in Louisville, KY.